Package substrate and method for fabricating the same

Abstract

A package substrate and a method for fabricating the same are provided according to the present invention. The package substrate includes: a substrate body with a die attaching side and a ball implanting side lying opposite each other, having a plurality of wire bonding pads and a plurality of solder ball pads respectively, and having a first insulating passivation layer and a second insulating passivation layer respectively, wherein a plurality of first apertures and a plurality of second apertures are formed in the first insulating passivation layer and the second insulation passivation layer respectively to corresponding expose the wire bonding pads and the solder ball pads; a chemical plating metal layer formed on the wire bonding pads and solder ball pads respectively; and a wire bonding metal layer formed on a surface of the chemical plating metal layer of the wire bonding metal layer.

1. A fabrication method of a package substrate, comprising the steps of:
 a substrate body having a die attaching side and a ball implanting side opposite to the die attaching side, wherein the die attaching side is formed with a plurality of wire bonding pads, and is covered with a first insulating passivation layer being formed with a plurality of first apertures for exposing the wire bonding pads, and wherein the ball implanting side is formed with a plurality of solder ball pads and is covered with a second insulating passivation layer being formed with a plurality of second apertures for exposing the solder ball pads; 
 forming a chemical plating metal layer on the wire bonding pads and the solder ball pads respectively; 
 forming a first conductive layer on the first insulating passivation layer and the chemical plating metal layer on the wire bonding pads; 
 forming a first photoresist layer on the first conductive layer, and forming a plurality of first openings in the first photoresist layer to expose the first conductive layer corresponding in position to the wire bonding pads, wherein the first openings are smaller in diameter than the first apertures so that a part of the first conductive layer on the wire bonding pads is covered by the first photoresist layer; 
 removing the first conductive layer exposed from the first openings to expose the chemical plating metal layer on the wire bonding pads; 
 forming a third photoresist layer on the first photoresist layer, and forming in the third photoresist layer a plurality of third openings smaller in diameter than the first openings so as to expose the chemical plating metal layer on the wire bonding pads; 
 forming a wire bonding metal layer on the chemical plating metal layer on the wire bonding pads by electroplating; and 
 removing the third photoresist layer, the first photoresist layer, and the first conductive layer under the first photoresist layer so as to expose the first insulation passivation layer and the wire bonding metal layer on the wire bonding pads inside the first apertures. 
 
   
   
     2. The fabrication method of a package substrate of  claim 1 , wherein the chemical plating metal layer is made of a material selected from the group consisting of nickel/gold (Ni/Au) and nickel/palladium/gold (Ni/Pd/Au), the gold being formed outermost. 
   
   
     3. The fabrication method of a package substrate of  claim 1 , further comprising the step of forming a second conductive layer on the second insulating passivation layer and the chemical plating metal layer on the solder ball pads. 
   
   
     4. The fabrication method of a package substrate of  claim 1 , wherein the conductive layer is formed by one of chemical deposition and physical deposition. 
   
   
     5. The fabrication method of a package substrate of  claim 1 , wherein the first conductive layer is made of copper (Cu). 
   
   
     6. The fabrication method of a package substrate of  claim 1 , wherein the wire bonding metal layer is made of gold (Au).